Forming thick wall skid plate?

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mcman56
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Forming thick wall skid plate?

Post by mcman56 » Fri May 28, 2004 1:11 pm

I need to make a skid plate for an off road bike out of something like 1/4" Aluminium. It is not a simple flat or curved plate so it would need some forming. (I'll try and attach a picture of something similar.) I do have the original thin steel skid plate as a guide but the new one would be a little wider. What kind of process is used to produce something like this in a quantity of one? What alloy should be used? Is there a soften/ harden process? I have read some sheet metal books showing forming with hammers but don't think it would apply to thick plate. Welding one up would be possible but my AL welding skills are very poor.

jpfalt
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Re: Forming thick wall skid plate?

Post by jpfalt » Fri May 28, 2004 5:03 pm

My suggestion would be to get some 6061T6 aluminum plate. It will be hardened, but you can solution anneal it to make it dead soft. Then you can work it with a domed punch over a maple form using a hydraulic press and it will form like butter.

After working it, you reharden it by baking in the oven.

mcman56
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Re: Forming thick wall skid plate?

Post by mcman56 » Sat May 29, 2004 12:07 pm

Thanks for the information. I do have access to a press. Where can I get details on the annealing and hardening?

D_R
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Re: Forming thick wall skid plate?

Post by D_R » Sun May 30, 2004 9:37 am

If you can't buy the material in a dead soft T0 condition you can anneal it yourself. Coat the surface with a felt tip marker or soot from an acetylene torch. Heat the plate with the torch just until the ink or soot is gone. Do both sides. (Note: I've never done 1/4" plate this way, but have done 1/8" quite few times. By doing both sides I think it'll work on 1/4") Practice on some scrap, you'll surprised how soft it gets. Be careful of melting the material, unlike steel aluminum doesn't give much warning before melting.

Do your forming with a domed tool over a wood form or even over a hard rubber piece.

The forming will work harden the material to some extent. The more severe the forming the more it'll work harden. With a fair amount of forming you may bring it up to T3 or 4 equivalent which might be harden enough.

If you get cracking in severely formed areas that'll indicate those areas need another annealing treatment midway through the forming process.

jpfalt
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Re: Forming thick wall skid plate?

Post by jpfalt » Sun May 30, 2004 6:10 pm

What I was referring to is solution annealing. You heat the plate to about 850 deg F and then quench in water. The aluminum will then be dead soft. After the cold working you harden by baking in an oven at about 400 degrees for one hour.

If you heat the plate and air cool, it will be in a condition called over aged. It will be softer, but will be more brittle than solution annealed. To reharden, it has to be solution annealed first.

Rod M1

Re: Forming thick wall skid plate?

Post by Rod M1 » Sun May 30, 2004 11:42 pm

You can get 6061-T0 at Aircraft Spruce.

http://www.aircraftspruce.com/catalog/m ... t_6061.php

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nic
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Re: Forming thick wall skid plate?

Post by nic » Mon May 31, 2004 12:35 am

Can you shoot a picture of the current skid plate? Maybe tack on some of your proposed extensions with masking tape and paper. This will give us an idea of how much you might need to form the material and thus the amount that it will need to be softened.

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MikeC
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Re: Forming thick wall skid plate?

Post by MikeC » Tue Jun 01, 2004 1:14 am

Have you considered titanium? As long as this piece isn't going to be welded on, you can probably make it easier out of light guage titanium than the 1/4" aluminum. It can be as thin as the steel, just as strong, and 1/3 the weight. I have learned that it is not as hard to work with as many think, and you can buy it as surplus drops for about the same price as high grade aluminum or 4130 (try titaniumjoe.com). Since this is not in a stressed situation, you can heat it to bend it, in which case it forms more easily than steel or aluminum. DO NOT heat aluminum and try to bend it. It is hot short and will crack on you.
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mcman56
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Re: Forming thick wall skid plate?

Post by mcman56 » Wed Jun 02, 2004 3:14 pm

Titanium is an interesting idea. When heated does it form like heated steel? (I have been trying to figure out a how before doing a detailed design or mock up.)

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Marcus
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Re: Forming thick wall skid plate?

Post by Marcus » Thu Jun 03, 2004 5:37 am

Hi MCMAN,

Just what are you trying to achieve? Do you want to provide further protection to the engine of the bike? Do you want a plate that will slide over obstacles without catching? Do you want to make it pretty? All of these may have a different solution to just using a larger/thicker plate. Often one can get blinded by finding an approach to solve a preconceived solution rather that posing the problem for a think tank approach. I think this forum can help you on both accounts and maybe with something very innovative. Worth a try me thinks.

D_R
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Re: Forming thick wall skid plate?

Post by D_R » Thu Jun 03, 2004 9:23 pm

Mike C. wrote: "DO NOT heat aluminum and try to bend it. It is hot short and will crack on you. "

Aluminum is heated to form it all the time, very common. It's routinely done for dimpling aircraft skins for rivets. I believe you only have to go 400 or 500 F to get significant improvement in forming.

What does "hot short" mean?

jpfalt
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Re: Forming thick wall skid plate?

Post by jpfalt » Fri Jun 04, 2004 12:49 am

Hot short means that the material loses the ability to stretch before it cracks. A term used in foundry is hot tear. Usually it's the result of an alloy that has parts of it start to melt before the rest. Metals of this type go through a mushy state when solidifying. The parts of the metal that melt first lose tensile strength and the material cracks rather than stretches

In some metals like titanium there is a change in the shape of the metal crystals that affects the ductility of the material. In titanium there is a critical range where the material gets very brittle. Above and below that range the metal stretches and forms well..

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